1 /*
2 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package javax.lang.model.util;
27
28 import javax.lang.model.element.*;
29 import javax.annotation.processing.SupportedSourceVersion;
30 import static javax.lang.model.element.ElementKind.*;
31 import javax.lang.model.SourceVersion;
32 import static javax.lang.model.SourceVersion.*;
33
34
35 /**
36 * A simple visitor of program elements with default behavior
37 * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
38 * source version.
39 *
40 * Visit methods corresponding to {@code RELEASE_6} language
41 * constructs call {@link #defaultAction}, passing their arguments to
42 * {@code defaultAction}'s corresponding parameters.
43 *
44 * <p> Methods in this class may be overridden subject to their
45 * general contract. Note that annotating methods in concrete
46 * subclasses with {@link java.lang.Override @Override} will help
47 * ensure that methods are overridden as intended.
48 *
49 * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
50 * implemented by this class may have methods added to it in the
51 * future to accommodate new, currently unknown, language structures
52 * added to future versions of the Java™ programming language.
53 * Therefore, methods whose names begin with {@code "visit"} may be
54 * added to this class in the future; to avoid incompatibilities,
55 * classes which extend this class should not declare any instance
56 * methods with names beginning with {@code "visit"}.
57 *
58 * <p>When such a new visit method is added, the default
59 * implementation in this class will be to call the {@link
60 * #visitUnknown visitUnknown} method. A new simple element visitor
61 * class will also be introduced to correspond to the new language
62 * level; this visitor will have different default behavior for the
63 * visit method in question. When the new visitor is introduced, all
64 * or portions of this visitor may be deprecated.
65 *
66 * @param <R> the return type of this visitor's methods. Use {@code Void}
67 * for visitors that do not need to return results.
68 * @param <P> the type of the additional parameter to this visitor's methods. Use {@code Void}
69 * for visitors that do not need an additional parameter.
70 *
71 * @author Joseph D. Darcy
72 * @author Scott Seligman
73 * @author Peter von der Ahé
74 *
75 * @see SimpleElementVisitor7
76 * @since 1.6
77 */
78 @SupportedSourceVersion(RELEASE_6)
79 public class SimpleElementVisitor6<R, P> extends AbstractElementVisitor6<R, P> {
80 /**
81 * Default value to be returned; {@link #defaultAction
82 * defaultAction} returns this value unless the method is
83 * overridden.
84 */
85 protected final R DEFAULT_VALUE;
86
87 /**
88 * Constructor for concrete subclasses; uses {@code null} for the
89 * default value.
90 */
91 protected SimpleElementVisitor6(){
92 DEFAULT_VALUE = null;
93 }
94
95 /**
96 * Constructor for concrete subclasses; uses the argument for the
97 * default value.
98 *
99 * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
100 */
101 protected SimpleElementVisitor6(R defaultValue){
102 DEFAULT_VALUE = defaultValue;
103 }
104 /**
105 * The default action for visit methods. The implementation in
106 * this class just returns {@link #DEFAULT_VALUE}; subclasses will
107 * commonly override this method.
108 *
109 * @param e the element to process
110 * @param p a visitor-specified parameter
111 * @return {@code DEFAULT_VALUE} unless overridden
112 */
113 protected R defaultAction(Element e, P p) {
114 return DEFAULT_VALUE;
115 }
116
117 /**
118 * {@inheritDoc} This implementation calls {@code defaultAction}.
119 *
120 * @param e {@inheritDoc}
121 * @param p {@inheritDoc}
122 * @return the result of {@code defaultAction}
123 */
124 public R visitPackage(PackageElement e, P p) {
125 return defaultAction(e, p);
126 }
127
128 /**
129 * {@inheritDoc} This implementation calls {@code defaultAction}.
130 *
131 * @param e {@inheritDoc}
132 * @param p {@inheritDoc}
133 * @return the result of {@code defaultAction}
134 */
135 public R visitType(TypeElement e, P p) {
136 return defaultAction(e, p);
137 }
138
139 /**
140 * {@inheritDoc} This implementation calls {@code defaultAction}.
141 *
142 * @param e {@inheritDoc}
143 * @param p {@inheritDoc}
144 * @return the result of {@code defaultAction}
145 */
146 public R visitVariable(VariableElement e, P p) {
147 return defaultAction(e, p);
148 }
149
150 /**
151 * {@inheritDoc} This implementation calls {@code defaultAction}.
152 *
153 * @param e {@inheritDoc}
154 * @param p {@inheritDoc}
155 * @return the result of {@code defaultAction}
156 */
157 public R visitExecutable(ExecutableElement e, P p) {
158 return defaultAction(e, p);
159 }
160
161 /**
162 * {@inheritDoc} This implementation calls {@code defaultAction}.
163 *
164 * @param e {@inheritDoc}
165 * @param p {@inheritDoc}
166 * @return the result of {@code defaultAction}
167 */
168 public R visitTypeParameter(TypeParameterElement e, P p) {
169 return defaultAction(e, p);
170 }
171 }